The present invention relates to spinal stabilization, and more particularly to dynamic spinal stabilization.
Numerous systems have been developed for stabilizing the vertebral column so as to promote healing, reduce pain, and/or allow for spinal fusion. Typical systems involve anchor members (e.g., polyaxial screws) secured to consecutive vertebrae, with a spinal rod rigidly fixed to the anchor members. The anchor members are typically screwed into the posterior portions of the vertebrae and pass through the pedicles and a substantial portion of the vertebral bodies and therefore provide a fixed and durable connection. The spinal rods are then clamped to the anchor members in a conventional fashion, creating a rigid stabilization structure. In most situations, one such structure is provided on each lateral side of the spine.
While such structures hold the vertebrae correctly positioned relative to each other, they tend to considerably stiffen the spine. This may significantly limit the patient's post-operative freedom of movement and/or may lead to undesirable loadings on nearby vertebrae. Accordingly, efforts have been made to develop stabilization approaches that can tolerate some movement, with the resulting systems typically referred to as dynamic spinal stabilization systems. Examples of dynamic stabilization systems are shown in U.S. Pat. No. 5,672,175 to Martin and U.S. Patent Application Publication No. 2005/0171540 to Lim et al.
While the prior art dynamic spinal stabilization systems, such as the Martin and Lim et al. systems, allow for dynamic spinal stabilization, they may not be entirely satisfactory in some situations. Thus, there remains a need for alternative approaches to dynamic spinal stabilization, advantageously approaches that allow for easy installation while remaining robust in use.